Human 2-defensin 3 (HBD3), a cationic antimicrobial peptide in human mucosal secretions, may attenuate the production of pro-inflammatory cytokines to microbial antigens. Such a mechanism would be a highly desirable event at oral mucosal surfaces that are continually exposed to microbial antigens from commensal flora and opportunistic pathogens. This hypothesis is tested using recombinant hemagglutinin B (rHagB) and recombinant Fimbrillin (rFimA), two adhesins from Porphyromonas gingivalis. This application brings together investigators whose long-term goals are to increase understanding of the human mucosal immune system, particularly the ability of defensins to attenuate cytokine responses. The objective is to evaluate the ability of HBD3 to act as a small molecule inhibitor attenuating pro-inflammatory cytokine responses to P. gingivalis adhesins. Our central hypothesis is that HBD3 binds to rHagB and rFimA and this interaction interrupts or alters the ability of rHagB and rFimA to induce pro-inflammatory cytokine responses via Mitogen Activated Protein Kinase (MAPK) pathways. Aim 1 will determine the ability of HBD3 to attenuate the pro- inflammatory cytokine response and MAPK response of human keratinocytes, monocytes, and myeloid dendritic cells to rHagB and rFimA. Pro-inflammatory cytokines in supernatants and MAPK phosphoproteins in lysates of cells exposed to HBD3 and rHagB or rFimA mixtures will be determined with and without signal transduction pathway inhibitors. Aim 2 will determine the ability of HBD3 to bind to rHagB and rFimA. The inhibition of rHagB or rFimA binding to cells by HBD3 will be determined by confocal microscopy and electron microscopy. The identity of rHagB and rFimA receptors on cell membranes will be identified using two-dimensional fluorescence difference gel electrophoresis (2-D DIGE). The ability of HBD3 or fragments of HBD3, to inhibit the binding of rHagB or rFimA to isolated receptor(s) will be determined by surface plasmon spectroscopy and ELISA. Aim 3 will determine the ability of HBD3 to attenuate a pro- inflammatory cytokine response in mice exposed to HBD3 and rHagB or rFimA mixtures. This work is relevant to public health and the mission of NIDCR. It will identify new mechanisms to suppress pro-inflammatory cytokine production and inhibit MAPK signaling pathways. This information would potentially provide a variety of new therapeutic avenues to control the inflammatory response related to oral infections. PUBLIC HEALTH RELEVANCE: Mechanisms that attenuate pro-inflammatory cytokine production and inhibit Mitogen Activated Protein Kinase (MAPK) signaling pathways are currently under investigation and serve as targets to improve therapies to treat a wide variety of diseases and inflammatory disorders. In this proposal, we present a new and exciting finding: human 2-defensin 3 (HBD3) serves as an upstream suppressor of cytokine signaling that binds to recombinant hemagglutinin B (rHagB) and recombinant Fimbrillin (rFimA) from Porphyromonas gingivalis strain 381 and attenuates pro-inflammatory cytokine responses. This finding is relevant to public health, relevant to the mission of NIDCR, and will provide a variety of new therapeutic avenues for treatment and prevention of the inflammatory response related to oral infections.